Z. Y. Xie

Effects of the Addition of Silane during Carbonization on the Epitaxy of 3C-SiC on Si

By supplying anothe source of Si during the carbonization step the Si out-diffusion was suppressed and the voids eliminated. Analysis was performed on both carbonized layers and ∼ I μm grown layers on Si(100) and (111) substrates to compare the results of carbonization with and without silane. Atomic force microscopy (AFM) images of the carbonized layer on Si(100) revealed that the pits present in the layer carbonized without silane could be suppressed hy introducing a small amount of silane (Si/C = 0.05) during the carbonization step. The root-mena-square (rms) roughness of the (100) carbonized layer was reduced from 4.9 to 0.3 nm at this Si to C ratio. AFM images of the Si(111) samples were less conclusive. Scanning electron microscopy (SEMI images of the ∼ 1 μm 3C-SiC epitaxial layers revealed that carbonizing with silane (Si/C = 0.06) improved the 3C-SiC/Si interfaces of both the (100) and (111) samples: the voids at the interface were completely eliminated. SEM images and AFM analysis of the 3C-SiC epitaxial layers showed that the surfaces were smoother when silane was added. X-ray diffraction (XRD) results revealed that there is no significant improvement in the crystal quality of the grown layers. Nevertheless, the reduction in surface roughness is beneficial for device fabrication or subsequent heteroepitaxy, such as zine blende GaN on 3C-SiC/Si(100).

Low temperature chemical vapor deposition of 3C-SiC on 6H-SiC — high resolution X-ray diffractometry and synchrotron X-ray topography study

Abstract Highly perfect 3C-SiC thin films, deposited on 6H-SiC by the chemical vapor deposition at low temperature with various Cl/Si, H/Si and C/Si ratios, were characterized by X-ray high resolution triple crystal diffractometry, synchrotron white beam X-ray topography (SWBXT) and synchrotron grazing incidence topography (SGIT) methods. The films were epitaxial with a low defect density (mostly in the range of 10 7 cm −2 ). The best films were produced with optimum C/Si ratio in the gas phase while the poorest quality films were produced at lower H 2 /Si ratio. Synchrotron topography revealed defects like cellular dislocation structure, super screw dislocations, pores, low angle grain boundaries and double positioning boundaries.

Effects of Surface Preparation on Epitaxial GaN on 6H-SIC Deposited Via Mocvd

A comparison was made of 6H-SiC surfaces etched with H 2, C2H4/H2, and HCl/H2, and the resulting crystal quality of epitaxial GaN films deposited on these substrates. To remove the many fine scratches and to smooth the rough surfaces typical of commercial SiC substrates, the Si-face 6H-SiC substrates were etched in H 2, C2H4/H2, and HCl/H2 at 1450 C. GaN was subsequently deposited on these etched surfaces after first depositing a low temperature GaN buffer layer via metalorganic chemical vapor deposition (MOCVD). The surface morphologies after etching and after GaN deposition were characterized by atomic force microscopy and Normaski differential interference contrast microscopy, while the crystal quality of the GaN films was assessed by double crystal x-ray rocking curves and x-ray topography. 6H-SiC substrate surfaces were improved in terms of the removal of scratches and the reduction of surface roughness, and both surface morphology and crystal quality of the subsequently deposited GaN films were enhanced. However, the dislocation density was not decreased by the surface etching. The best GaN film was produced by etching the substrate in pure H 2 fo 40 minutes before growth. Recommendations for the optimum substrate treatment are made.

Low Temperature Chemical Vapor Deposition Of 3C-SiC On 6H-SiC – An X-Ray Triple Crystal Diffractometry And X-Ray Topography Study

Highly perfect 3C-SiC thin films, on 6H-SiC deposited by the chemical vapor deposition at low temperature with various Cl/Si, H/Si and C/Si ratios were characterized by x-ray high resolution triple crystal diffractometry and double crystal topographic methods. The films were epitaxial with a low defect density present (mostly in the range of 10 7 /cm 2 ). X-ray topography revealed stacking faults, low angle grain boundaries, dislocations and inversion double positioning boundaries present in the film and substrate.

Growth and Characterization of B x Ga l-x N on 6H-SiC (0001) by MOVPE

Boron was incorporated into GaN in order to determine its limits of solubility, its ability of reducing the lattice constant mismatch with 6H-SiC, as well as its effects on the structural and optical properties of GaN epilayers. B x Ga l-x N films were deposited on 6H-SiC (0001) substrates at 950 °C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. A single phase alloy with x=0.015 was successfully produced at a gas reactant B/Ga ratio of 0.005. Phase separation into pure GaN and B x Ga l-x N alloy with x=0.30 was deposited for a B/Ga reactant ratio of 0.01. This is the highest B fraction of the wurtzite structure alloy ever reported. For B/Ga ratio ≥ 0.02, no B x Ga l-x N was formed, and the solid solution contained two phases: wurtzite GaN and BN based on the results of Auger and x-ray diffraction. The band edge emission of B x Ga l-x N varied from 3.451 eV for x=0 with FWHM of 39.2 meV to 3.465 eV for x=0.015 with FWHM of 35.1 meV. The narrower FWHM indicated that the quality of GaN epilayer was improved with small amount of boron incorporation.